Design a temporary soldier beam and lagging system to accommodate a 18' cut in dense silt required to construct a foundation for a midrise concrete structure. The rectangular excavation will be supported by soldier beams spaced on 8' centers with timber lagging installed behind the front (near) flanges. Select an appropriate wide flange beam (W-shape) and the appropriate rough sawn SYP timber lagging where Fb = 1,700 psi. Include a row of tiebacks on walers approximately 6' below original ground in between soldier beams in alternating (every other) bays. Include a lateral pressure of 72 psf due to surcharge. Be sure to design for the maximum lateral pressure during installation (before the tiebacks are installed) and service (the subgrade reaches 18' below the original ground). Find: 1) an economic wide flange section for the soldier beam. 2) the lagging thickness. Hints: 1) Dense silt, = 27. Unit weight = 120 pcf. 2) Assume the (maximum) lateral earth pressure acts as a uniform rectangular loading. 3) Each of the soldier beams has a single anchor. You should know how to calculate Mmax. 4) Use Fb = 22,000 psi for the soldier beam. 5) The hinge point of the soldier beam